Refurbishing corroded steel structures with VpCI® CorrVerter®Anna Lee
One problem that Cortec runs across fairly frequently is addressing old and corroded structures that have steel reinforcement. This can be found in large old buildings or structures such as bridges, parking ramps and towers. In many cases going in and replacing or mechanically repairing rusted steel is not viable. If steel continues to rust, eventually mechanical integrity will suffer. Rusted steel played a role in the 35W bridge collapse in the summer of 2007. In 2005 that bridge was inspected and categorized as structurally deficient because of significant corrosion present. It should be stated that while corrosion was a factor, the main cause was ultimately identified as a design flaw where support plates should have been ½” thicker to meet engineering standards for the expected life time load.
Cortec has a product known as VpCI® CorrVerter®. When this product is applied to rusted steel, the rust is actually transformed into a protective layer. VpCI® CorrVerter® penetrates all the way into the bare metal. We are not implying that VpCI® CorrVerter® would have prevented the 35W bridge disaster since the main issue was design, but it would have stopped and retarded further corrosion of those plates.
One such structure where VpCI® CorrVerter® was successfully used was the famous Zagreb Cathedral. The Zagreb Cathedral is one of the tallest buildings in Croatia and is almost 1000 years old. A refurbishing project was initiated in 2012. During reconstruction work on the south tower, steel bands with a high level of corrosion were observed. Replacing these bands would require significant intrusion of the structure. After a team of local scientists and engineers examined and tested the bands, they recommended removing the loose corrosion and the application of an anti-corrosion product.
Cortec VpCI® CorrVerter® was chosen for this project because of its outstanding properties. After brushing the bands to remove loose rust, two layers of the material were applied by a combination of brushing and spraying. VpCI® CorrVerter® is a water based product that quickly converts rust into a protective layer. It contains a chemical chelating agent that modifies the surface rust into a hydrophobic passive layer and is capable of penetrating into the depths of the corroded layer.
The entire project was completed successfully with minimal cost; the coating penetrated to the non-corroded layer of the steel and stopped the corrosion process.
It is doubtful that any of Packet’s clients will be refurbishing cathedral towers, but corrosion issues for structural steel beams or cabling are common. In these cases, Packet can help provide an effective, low cost solution that is environmentally friendly.